1. Field of the Invention
The present invention relates to an optical information accessing system for a disc-type recording medium such as an optical disc including a plurality of tracks forming one helix, and more particularly, to the improvement of a jump-back control of the optical information accessing system.
2. Description of the Related Art
In an optical disc having a plurality of tracks forming one helix, an optical head traces the helix. In this case, when data processing upon one of the tracks is abnormally interrupted, it is necessary for the optical head to retrace the same track. In other words, after the optical disc is rotated one revolution, the optical head is required to jump-back to the same track. This is called a jump-back operation.
In a prior art optical information accessing system, any jump-back operation is carried out at a special sector of each of the tracks. In this case, the special sectors are located at the same radius position of the optical disc. Therefore, when the data processing is incomplete for the special sector, a jump-back operation is carried out after another revolution of the optical disc, which may invite a jump-back operation for other tracks shifted from a track which requires such a jump-back operation.